Methods and systems for exchanging information in an integrated access and backhaul system

ABSTRACT

Methods, apparatus, and systems for reducing packet loss in wireless systems during handover, where one or more user equipment or mobile terminals are connected to an integrated access and backhaul node. The disclosure relates to continuing uplink (UL) and maintain service continuity in an integrated access and backhaul (IAB) system.

CROSS REFERENCE TO RELATED APPLICATIONS

This patent document is a continuation of and claims benefit of priorityto International Patent Application No. PCT/CN2020/105775, filed on Jul.30, 2020. The entire contents of the before-mentioned patentapplications are incorporated by reference as part of the disclosure ofthis application.

TECHNICAL FIELD

This disclosure is directed generally to wireless communications.

BACKGROUND

Mobile communication technologies are moving the world toward anincreasingly connected and networked society. The rapid growth of mobilecommunications and advances in technology have led to greater demand forcapacity and connectivity. Other aspects, such as energy consumption,device cost, spectral efficiency, and latency are also important tomeeting the needs of various communication scenarios. Varioustechniques, including new ways to provide higher quality of service,longer battery life, and improved performance are being discussed.

SUMMARY

This patent document describes, among other things, techniques forcommunicating in an integrated access and backhaul (IAB) deployment forNew Radio (NR).

The following aspects may be preferably implemented in variousembodiments.

In an aspect, one or more IAB nodes are communicatively coupled to afirst parent node or a second parent node and one or more child nodes,wherein the parent node is communicatively coupled to a first IAB donorCentral Unit (CU).

In an aspect, one or more IAB nodes receive a RRCreconfigurationmessage, or a stop indication, or a handover indication. In yet anotheraspect, the IAB node sends to a child IAB node sends a stop indicationor a handover indication wherein the stop indication or the handoverindication indicates that the child node should stop data forwarding. Inyet another embodiment, the IAB node is an IAB donor central unit (CU).

In an aspect, one or more IAB nodes, receives a stop indication in aF1AP message, wherein the F1AP message includes a RRCreconfigurationmessage, and stop the forwarding of User Equipment (UE) data packets.

In an aspect, one or more IAB nodes include a flag in BAP header of theUser Equipment (UE) packet, and transmit the UE packet to the next hop,wherein the flag indicates that the next hop ignores the BAP header orselects any net hop or selects any egress backhaul (BH) RLC channel todeliver the packets.

In an aspect, one or more IAB nodes, send uplink (UL) delivery statusinformation to at least one or more child nodes. In yet another aspect,the UL delivery status information comprises sequence numbers (SNs) ofone or more packets that are received from one of the one or more childnodes, where the one or more packets have not been sent to the firstparent node or have not been confirmed as received by the first parentnode. In yet another aspect, the UL delivery status information is sentvia a BAP sublayer control PDU or BAP sublayer data unit or a RLCsublayer control PDU. In yet another aspect, the UL delivery statusinformation includes at least one of a RLC SN, a RLC channel ID orLogical Channel (LC) ID, a backhaul (BH) RLC channel ID, or a BAPsublayer SN. In yet another aspect, one or more IAB nodes, send one ormore data packets that need to be re-transmitted to at least one of theone or more child nodes, wherein the one or more data packets contain atleast one of a source IAB node's BAP address, an access node's BAPaddress and a flag in a BAP sub header. In yet another aspect, thebackhaul RLC channel for transmitting the one or more data packets isconfigured by donor CU.

In an aspect, one or more IAB nodes receive a UL transfer status from asecond IAB donor CU, wherein the UL transfer status is transmitted afterthe second IAB donor CU receives a SN transfer message, and retransmitpackets according to the UL transfer status. In yet another embodiment,the UL transfer status contains at least one of the receive status ofthe UL PDCP SDU and UL COUNT value of the first missing UL SDU.

In an aspect, one or more IAB nodes include a flag in the GTP-U headerof one or more packets, wherein the flag indicates that the packets needto be forwarded to a first IAB donor central unit (CU) and transmit theone or more packets to the next hop.

In another aspect, one or more IAB nodes transmit an end marker viaGTP-U layer or F1AP message to a second IAB donor CU after receiving astop indication in F1AP message. In yet another aspect, the second IABdonor CU sends the end marker to the first IAB donor CU.

In yet another aspect, a donor CU sends to one or IAB nodes a stopindication in a F1AP message, wherein the F1AP message includes aRRCreconfiguration message, wherein the stop indication indicates theone or more IAB nodes to stop the forwarding of User Equipment (UE) datapackets.

In yet another embodiment, a IAB node receives from one or more parentIAB nodes, uplink (UL) delivery status information. In yet anotherembodiment, UL delivery status information comprises sequence numbers(SNs) of one or more packets that are received from one of the one ormore child nodes, where the one or more packets have not been sent tothe first parent node or have not been confirmed as received by thefirst parent node. In yet another embodiment, the UL delivery statusinformation is sent via a BAP sublayer control PDU or BAP sublayer dataPDU or a RLC sublayer control PDU. In yet another embodiment, the ULdelivery status information includes at least one of a RLC SN, a RLCchannel ID or Logical Channel (LC) ID, a backhaul (BH) RLC channel ID,or a BAP sublayer SN.

In an aspect, an IAB node receives from one or more IAB nodes, one ormore data packets that need to be re-transmitted, wherein the one ormore data packets contain at least one of a source IAB node's BAPaddress, an access node's BAP address and a flag in a BAP subheader. Inyet another aspect, the backhaul RLC channel for the one or more datapackets is configured by donor CU.

In an aspect, a second IAB donor CU transmits to one or more IAB nodes,a UL transfer status, wherein the UL transfer status is transmittedafter the second IAB donor CU receives a SN transfer message from thefirst IAB donor CU, wherein the one or more IAB nodes are configured todetermine which packets need to be retransmitted according to the ULtransfer status. In yet another aspect, the UL transfer status containsat least one of the receive status of the UL PDCP SDU and UL COUNT valueof the first missing UL SDU.

In yet another aspect, a first IAB donor CU receives from one or moreIAB nodes, one or more packets that include a flag in the GTP-U headerof the one or more packets, wherein the flag indicates that the packetsneed to be forwarded to a first IAB donor central unit (CU).

In another aspect, a second IAB donor CU receives an end marker viaGTP-U layer or F1AP message, wherein the end marker is usable by asecond IAB donor CU to cease forwarding of one or more packets to thefirst IAB donor CU. In yet another aspect, the second IAB donor CU sendsthe end marker to the first IAB donor CU.

In aspects of the disclosure, the transmission and reception of messagesis performed by various devices, including MT, UE, IAB nodes (e.g.,access, migrating, descendant, or ancestor), and IAB donors.

These, and other, aspects are described in the present disclosure.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 illustrates an embodiment of an IAB deployment in a moveablevehicle.

FIG. 2 illustrates an embodiment of an IAB topology.

FIG. 3 illustrates an IAB topology where handover of an IAB node isperformed.

FIG. 4 illustrates an IAB topology where handover of an IAB node isperformed.

FIG. 5 illustrates an embodiment where UL data transfer of a descendantnode or UE is managed.

FIG. 6 illustrates an embodiment where the UL data transfer of adescendant node or UE are managed.

FIG. 7 illustrates another embodiment that manages retransmission ofpackets.

FIG. 8 illustrates an embodiment where a node determines the packets tobe retransmitted.

FIG. 9 illustrates an embodiment illustrating the retransmission ofpackets.

FIG. 10 illustrates an embodiment where packets that need to beforwarded from a target to a source donor are identified.

FIG. 11 shows an example of a wireless communication system wheretechniques in accordance with one or more embodiments of the presenttechnology can be applied.

FIG. 12 is a block diagram representation of a portion of a radiostation in accordance with one or more embodiments of the presenttechnology can be applied.

DETAILED DESCRIPTION

The disclosure relates to wireless systems. More specifically, itrelates to reducing packet loss during handover in a IAB deployment.

For instance, an integrated access and backhaul (IAB) system supportswireless backhauling by deploying new radio (NR) cells to reduce theneed for wireline transport infrastructure.

The terminating node of the NR backhaul network on the network side iscommonly referred to as an IAB donor, which represents a gNB, which isthe logical node that has additional functionality to support IAB. AnIAB node supports gNB Distributed Unit (gNB-DU) functionality, whichallows NR access to user equipment (UE) and next-hop IAB nodes. The IABnode also supports functionality for IAB-MT, which allows connections tothe gNB-DU of another IAB node or the IAB donor.

In one example, as shown in FIG. 1 , a moveable vehicle, such as a highspeed train 101 has several passengers with one or more mobile terminal(MT) or user equipment (UE) 103-106. The UE 103-106 are wirelesslyconnected to an IAB node 102, and the IAB node 102 is in turn connectedto a donor node or a parent IAB node 107 or 108. As the high speed trainmoves, handover between parent IAB nodes occurs. The UE 103-106 accessesthe network via the IAB node 102, and the IAB node 102 accesses thenetwork via a parent IAB node. Here, it should be understood that theusage of UE and MT are not mutually exclusive, and one should presumethat either term can refer to either a MT or UE. It should also beunderstood that a parent IAB node should be understood to be encompassedby the term base station. It should be understood that, although amoveable vehicle has been discussed, the techniques disclosed herein arealso applicable to static IAB nodes, which may want to perform migrationdue to load balance or due to Back Haul Radio Link Failure (BH RLF).

The relative positions between the UEs 103-106 and the IAB node 102 willchange little as the train 101 travels across. However, the relativeposition between the IAB node 102 and each IAB donor will changefrequently when the train 101 travels.

Consequently, this disclosure provides systems and methods performinghandover of the IAB node 102 can be performed. This reduces signalingoverhead and improves service continuity.

FIG. 2 illustrates an IAB topology. Parent nodes 201 and 202 have IAB-DUfunctionality, and they provide NR access to an IAB node 203. IAB node203 has functionality as both an IAB MT and as an IAB DU. IAB node 203can connect to parent nodes 201 and 202 as a IAB MT, and also provideaccess to child nodes 204-206 as a IAB DU. Child nodes 204-206 havefunctionality of an IAB MT. As can be understood, any node in thetopology can work as a donor or a terminal, so long as it is designedwith that functionality.

FIG. 3 illustrates an IAB topology where handover of an IAB node isperformed. UE 302 is wirelessly coupled to an IAB node 304, which iswirelessly coupled to IAB node 306. A UE 308 is coupled to IAB node 306.It should be understood that any number of UE or MT can be coupled toany of the IAB nodes.

As denoted from arrow 322, IAB node 306 is migrating from IAB node 314to IAB node 312. IAB node 314 is coupled to IAB donor DU 318, and IABnode 312 is coupled to IAB donor DU 316. Both IAB donor 318 and 316 arecoupled to IAB donor CU.

FIG. 4 illustrates an IAB topology where handover of an IAB node isperformed. FIG. 4 differs from FIG. 3 in that there is a second IABdonor CU.

UE 402 is wirelessly coupled to an IAB node 404, which is wirelesslycoupled to IAB node 406. A UE 408 is coupled to IAB node 406. It shouldbe understood that any number of UE or MT can be coupled to any of theIAB nodes.

As denoted from arrow 422, IAB node 406 is migrating from IAB node 414to IAB node 412. IAB node 414 is coupled to IAB donor DU 418, and IABnode 412 is coupled to IAB donor DU 424. Both IAB donor 418 and 416 arecoupled to different IAB donor CUs. In the case of FIG. 4 , the IAB node406 not only migrates between IAB nodes, but also between IAB donor CUs.

It should be understood that the topologies disclosed are onlyexemplary. Any number of nodes, UEs, or donors can exist within an IABdeployment.

The topologies disclosed apply to the embodiments disclosed herein.

FIG. 5 illustrates an embodiment where UL data transfer of a descendantnode or UE is managed. In step 502 an RRCreconfiguration message, or astop indication, or a handover indication is received at an IAB node. Instep 504, the IAB node that received the message sends a stop indicationor a handover indication to a child node. It should be understood thatthe child node can be another IAB node, a UE, or a MT. In step 506, thenode that received the stop indication or handover indication stops dataforwarding to the IAB node. In an embodiment, the IAB node is a IABdonor central unit (CU).

In an embodiment, the access or intermediate IAB node buffers datapackets received from UE and transmit the buffered packets on the targetpath. In an embodiment, the IAB node starts to buffer data packets uponreceiving a stop indication (or handover initiation indication) fromparent node, and the IAB node sends the stop indication to the child MTupon receiving the stop indication from parent node. In an embodiment,the migrating IAB node sends the stop indication upon receiving HO CMD.

In an embodiment, UL transmission resumes upon the IAB node receiving aresume indication (or handover complete indication) from parent nodeafter the IAB node receives an updated F1-U UL mapping configuration. Inan embodiment, this option is used when the updated F1-U UL mappingconfiguration is sent via a HO CMD, where the IAB node sends the resumeindication to child MT upon receiving the resume indication from parentnode and the migrating IAB node sends the resume indication upon targetpath is ready.

FIG. 6 illustrates an embodiment where the UL data transfer of adescendant node or UE are managed. In step 602, an IAB node receives astop indication or a handover indication in a F1AP message. In anembodiment, the F1AP message includes a RRCreconfiguration message. Instep 604, the IAB stops the forwarding of UE data packets. In anembodiment, the DL RRC MESSAGE TRANSFER is an example of F1AP message.

In an embodiment, the UE shall send RRCreconfigurationcomplete and usethe new ciphering key after receiving HO cmd. In a further embodiment,the migrating IAB node may still connect to source parent node and, theIAB node shall stop forwarding RRCreconfigurationcomplete message andpackets ciphered with new keys on the source path, i.e., stop UL dataforwarding and buffer the data packets received for UE in order to avoidRRCreconfigurationcomplete/SCTP/F1 setup messages and UE packetsciphered with new keys are delivered to source donor CU. In anembodiment, the access IAB node stops the corresponding UE's UL dataforwarding upon receiving stop indication in DL RRC MESSAGE TRANSFERmessage which includes HO CMD for the UE.

FIG. 7 illustrates another embodiment that manages retransmission ofpackets. In step 702, a flag in a Backhaul Adaption Protocol (BAP)header is included in a UE packet. In step 704, the UE packet istransmitted to the next hop. The flag indicates that the next hopignores the BAP header or selects any next hop or any egress backhaul(BH) Radio Link Control (RLC) channel to deliver the UE packets.

In an embodiment, the BAP address and the BAP routing ID are changedafter migration of an IAB node from one parent node to another parentnode, and the IAB node and donor DU on the target path are unable toidentify the BAP routing ID contained in the BAP header of there-transmitted packets and may discard these packets. In an embodiment,to address this, the migrating IAB node includes a flag in BAP header ofthe re-transmitted packets, and the parent IAB node ignores the BAPheader or selects any next hop or selects any egress BH RLC channel todeliver the packets if the flag exists.

FIG. 8 illustrates an embodiment where a node determines the packets tobe retransmitted. In step 802, an IAB node sends UL delivery statusinformation to a child node. In an embodiment, the UL delivery statusinformation comprises sequence numbers (SNs) of the packets from thechild nodes that have not been sent to, nor have they been confirmed by,the IAB node's parent node. In an embodiment, the UL delivery statusinformation is sent via a BAP sublayer control PDU or BAP sublayer dataPDU or a RLC sublayer control PDU. In an embodiment, the UL deliverystatus information includes at least one of a RLC SN, a RLC channel IDor Logical Channel (LC) ID, a backhaul (BH) RLC channel ID, or a BAPsublayer SN. In step 804, the IAB node sends packets that need to beretransmitted to the child node. In an embodiment, the packets containat least a source IAB node's BAP address, an access node's BAP addressand a flag in a BAP subheader.

In an embodiment, the IAB access IAB node determines the packets thatneed to be retransmitted. The migrating/descendant IAB node sends the ULdelivery status information (e.g. SNs of packets which are received fromchild MT and not confirmed or not sent) to a child MT. Upon thereception of UL delivery status information, the child IAB node sendsthe SNs of packets which are received from its child MT and notconfirmed by RLC ACK to its child MT as well. The UL delivery statusinformation could be sent via BAP layer (e.g. BAP control PDU) or RLClayer (e.g. RLC control PDU), and includes at least one of thefollowing: RLC SN in the ingress link; RLC channel ID or LCID; BAP layerSN.

In an embodiment, the migrating/descendant IAB node sends SNs andpackets which needs to be re-transmitted on the target path to thedescendant node. The access IAB node's BAP address is also contained inthe BAP header. In an embodiment, a retransmission flag needs to becontained in the BAP header. Any BH RLC channel or channel by specificimplementation or channel via CU configuration are used.

FIG. 9 illustrates an embodiment illustrating the retransmission ofpackets. In step 902, an IAB node receives an UL transfer status from adonor IAB. In an embodiment, the UL transfer status is transmitted afterthe IAB donor CU receives a SN transfer message. In step 904, the IABnode retransmits packets according to the UL transfer status. In anembodiment, the UL transfer status contains at least one of the receivestatus of the UL PDCP SDU and UL COUNT value of the first missing ULSDU.

In an embodiment, after receiving the SN status transfer message (whichcan contain the Status Of PDCP SDU and UL COUNT Value per UE DRB) sentfrom source donor CU, a target donor CU sends the UL transfer status tothe access IAB node. The access IAB node could determine which packetsneed to be retransmitted according to the UL transfer status receivedfrom target donor CU.

FIG. 10 illustrates an embodiment where packets that need to beforwarded from a target to a source donor are identified. In step 1002,an IAB node includes a flag in the GTP-U header of one or more packets.In an embodiment, the flag indicates that the packets need to beforwarded to the source donor, e.g., to a particular donor CU. In step1004, the IAB node transmits the packets to the next hop.

FIG. 11 illustrates an embodiment where packets that need to beforwarded are identified. In step 1102, an IAB node receives a stopindication in an F1AP message. In step 1104, an IAB node transmits anend marker via a GTP-U layer or a FLAP message to a target donor CU. Inan embodiment, the target IAB donor (CU) sends the end marker to thesource IAB donor (CU).

In an embodiment, the target donor CU identifies the packets that needto be forwarded to source donor CU via an end marker. The UE applies thea new ciphering key after receiving HO CMD, and the access IAB nodesends an end maker after receiving DL RRC MESSAGE TRANSFER message(which includes HO CMD for the UE). Target donor CU forwards packetsreceived from migrating/descendant node to S-donor CU until it receivesend marker. In an embodiment, the donor CU shall be aware of the endmarker. In an embodiment, the end marker is sent per UE bearer or perUE. In an embodiment, the T-donor CU sends the end marker to the S-donorCU as well, and then the S-donor CU sends the SN status transfer message(which includes UL transfer status) to T-donor CU upon reception of theend marker.

In an embodiment, UL data transfer of descendant node and UE continueduring migration by an IAB node sending a stop/resume indication tochild IAB-MT. In an embodiment, UL data transfer of descendant node andUE continue during migration by a including a stop indication in a DLRRC MESSAGE TRANSFER message.

In an embodiment, the BAP address and BAP routing ID changed aftermigration, and the access IAB node includes a flag in BAP header of thepackets, where the IAB node ignores the BAP header and selects any nexthop or selects any egress BH RLC channel to deliver the packets if theflag exists.

In an embodiment, the access IAB node determines the packets that needto be re-transmitted or transmitted, by receiving the UL delivery statusinformation (e.g. SNs of packets which are received from child MT andnot confirmed or not sent) from the migrating IAB node and/orintermediate node. In an embodiment, the access IAB node determines thepackets that need to be re-transmitted or transmitted, by sending SNsand packets which needs to be re-transmitted on the target path to childIAB-MT. In an embodiment, the access IAB node determines the packetsthat need to be re-transmitted or transmitted, by containing the sourceIAB node's BAP address or access IAB node's BAP address in the BAPheader. In an embodiment, a retransmission flag can be contained in theBAP header. In an embodiment, the access IAB node determines the packetsthat need to be re-transmitted or transmitted, where the donor CUconfigures traffic mapping for packets needs to be retransmitted viaF1AP message. In an embodiment, the access IAB node determines thepackets that need to be re-transmitted or transmitted, after receivingSN status transfer message (contains Status Of PDCP SDU and UL COUNTValue per UE DRB) sent from source donor CU, target donor CU sends theUL transfer status to the access IAB node via F1.

In an embodiment, the target donor CU identifies which packets needs tobe forwarded to source donor CU by having a flag/end marker is containedin GTP-U header or the T-donor CU send end marker to S-donor CU so that,after receiving the end marker, the source donor CU could be made awarethat there is no more data forwarding from the target donor CU. In anembodiment, the access IAB node includes the flag/end marker in theGTP-U header.

It should be understood that, while some embodiments describe thetransmission of certain data to a node in the IAB deployment, that thedisclosure envisions the receipt and further transmission. For instance,where an IAB node is described as transmitting a piece of data intendedfor a UE, it should be understood that any number of child IAB nodesexist in between the IAB node transmitting the data and the UE. Itshould be understood that those IAB nodes likewise transmit that data.The same applies for any nodes in between the path of an IAB nodetransmitting data and the IAB donor CU.

FIG. 11 shows an example of a wireless communication system 1100 wheretechniques in accordance with one or more embodiments of the presenttechnology can be applied. A wireless communication system 1100 caninclude one or more base stations (BSs) 1105 a, 1105 b, one or morewireless devices 1110 a, 1110 b, 1110 c, 1110 d, and a core network1125. A base station 1105 a, 1105 b can provide wireless service towireless devices 1110 a, 1110 b, 1110 c and 1110 d in one or morewireless sectors. In some implementations, a base station 1105 a, 1105 bincludes directional antennas to produce two or more directional beamsto provide wireless coverage in different sectors. As should beunderstood, with reference to FIGS. 1 to 4 , the base stations can be aseries of IAB nodes.

The core network 1125 can communicate with one or more base stations1105 a, 1105 b. The core network 1125 provides connectivity with otherwireless communication systems and wired communication systems. The corenetwork may include one or more service subscription databases to storeinformation related to the subscribed wireless devices 1110 a, 1110 b,1110 c, and 1110 d. A first base station 1105 a can provide wirelessservice based on a first radio access technology, whereas a second basestation 1105 b can provide wireless service based on a second radioaccess technology. The base stations 1105 a and 1105 b may be co-locatedor may be separately installed in the field according to the deploymentscenario. The wireless devices 1110 a, 1110 b, 1110 c, and 1110 d cansupport multiple different radio access technologies. The techniques andembodiments described in the present document may be implemented by thebase stations of wireless devices described in the present document.

FIG. 12 is a block diagram representation of a portion of a radiostation in accordance with one or more embodiments of the presenttechnology can be applied. A radio station 1205 such as a base stationor a wireless device (or UE) or MT can include processor electronics1210 such as a microprocessor that implements one or more of thewireless techniques presented in this document. The radio station 1205can include transceiver electronics 1215 to send and/or receive wirelesssignals over one or more communication interfaces such as antenna 1220.The radio station 1205 can include other communication interfaces fortransmitting and receiving data. Radio station 1205 can include one ormore memories (not explicitly shown) configured to store informationsuch as data and/or instructions. In some implementations, the processorelectronics 1210 can include at least a portion of the transceiverelectronics 1215. In some embodiments, at least some of the disclosedtechniques, modules or functions are implemented using the radio station1205. In some embodiments, the radio station 1205 may be configured toperform the methods described herein.

It will be appreciated that the present document discloses techniquesthat can be embodied in various embodiments of IAB deployments. Thedisclosed and other embodiments, modules and the functional operationsdescribed in this document can be implemented in digital electroniccircuitry, or in computer software, firmware, or hardware, including thestructures disclosed in this document and their structural equivalents,or in combinations of one or more of them. The disclosed and otherembodiments can be implemented as one or more computer program products,i.e., one or more modules of computer program instructions encoded on acomputer readable medium for execution by, or to control the operationof, data processing apparatus. The computer readable medium can be amachine-readable storage device, a machine-readable storage substrate, amemory device, a composition of matter effecting a machine-readablepropagated signal, or a combination of one or more them. The term “dataprocessing apparatus” encompasses all apparatus, devices, and machinesfor processing data, including by way of example a programmableprocessor, a computer, or multiple processors or computers. Theapparatus can include, in addition to hardware, code that creates anexecution environment for the computer program in question, e.g., codethat constitutes processor firmware, a protocol stack, a databasemanagement system, an operating system, or a combination of one or moreof them. A propagated signal is an artificially generated signal, e.g.,a machine-generated electrical, optical, or electromagnetic signal, thatis generated to encode information for transmission to suitable receiverapparatus.

A computer program (also known as a program, software, softwareapplication, script, or code) can be written in any form of programminglanguage, including compiled or interpreted languages, and it can bedeployed in any form, including as a stand-alone program or as a module,component, subroutine, or other unit suitable for use in a computingenvironment. A computer program does not necessarily correspond to afile in a file system. A program can be stored in a portion of a filethat holds other programs or data (e.g., one or more scripts stored in amarkup language document), in a single file dedicated to the program inquestion, or in multiple coordinated files (e.g., files that store oneor more modules, sub programs, or portions of code). A computer programcan be deployed to be executed on one computer or on multiple computersthat are located at one site or distributed across multiple sites andinterconnected by a communication network.

The processes and logic flows described in this document can beperformed by one or more programmable processors executing one or morecomputer programs to perform functions by operating on input data andgenerating output. The processes and logic flows can also be performedby, and apparatus can also be implemented as, special purpose logiccircuitry, e.g., an FPGA (field programmable gate array) or an ASIC(application specific integrated circuit).

Processors suitable for the execution of a computer program include, byway of example, both general and special purpose microprocessors, andany one or more processors of any kind of digital computer. Generally, aprocessor will receive instructions and data from a read only memory ora random-access memory or both. The essential elements of a computer area processor for performing instructions and one or more memory devicesfor storing instructions and data. Generally, a computer will alsoinclude, or be operatively coupled to receive data from or transfer datato, or both, one or more mass storage devices for storing data, e.g.,magnetic, magneto optical disks, or optical disks. However, a computerneed not have such devices. Computer readable media suitable for storingcomputer program instructions and data include all forms of non-volatilememory, media and memory devices, including by way of examplesemiconductor memory devices, e.g., EPROM, EEPROM, and flash memorydevices; magnetic disks, e.g., internal hard disks or removable disks;magneto optical disks; and CD ROM and DVD-ROM disks. The processor andthe memory can be supplemented by, or incorporated in, special purposelogic circuitry.

While this patent document contains many specifics, these should not beconstrued as limitations on the scope of any invention or of what may beclaimed, but rather as descriptions of features that may be specific toparticular embodiments of particular inventions. Certain features thatare described in this patent document in the context of separateembodiments can also be implemented in combination in a singleembodiment. Conversely, various features that are described in thecontext of a single embodiment can also be implemented in multipleembodiments separately or in any suitable subcombination. Moreover,although features may be described above as acting in certaincombinations and even initially claimed as such, one or more featuresfrom a claimed combination can in some cases be excised from thecombination, and the claimed combination may be directed to asubcombination or variation of a subcombination.

Similarly, while operations are depicted in the drawings in a particularorder, this should not be understood as requiring that such operationsbe performed in the particular order shown or in sequential order, orthat all illustrated operations be performed, to achieve desirableresults. Moreover, the separation of various system components in theembodiments described in this patent document should not be understoodas requiring such separation in all embodiments.

Only a few implementations and examples are described, and otherimplementations, enhancements and variations can be made based on whatis described and illustrated in this patent document.

What is claimed is:
 1. An information transmission method comprising:sending, by an integrated access and backhaul (IAB) node, uplink (UL)delivery status information to at least one or more child nodes.
 2. Themethod according to claim 1, wherein the UL delivery status informationcomprises sequence numbers (SNs) of one or more packets that arereceived from one of the one or more child nodes, where the one or morepackets have not been transmitted to a parent node or have not beenconfirmed as received by the parent node.
 3. The method according toclaim 2, wherein the UL delivery status information is sent via aBackhaul Adaptation Protocol (BAP) sublayer control Protocol Data Unit(PDU) or BAP sublayer data PDU or a Radio Link Control (RLC) sublayercontrol PDU.
 4. The method according to claim 1, wherein the UL deliverystatus information includes at least one of a RLC SN, a RLC channel IDor Logical Channel (LC) ID, a backhaul (BH) RLC channel ID, or a BAPsublayer SN.
 5. The method according to claim 1, further comprising:sending, by the IAB node, one or more data packets that need to bere-transmitted to at least one of the one or more child nodes, whereinthe one or more data packets contain at least one of a source IAB node'sBAP address, an access node's BAP address and a flag in a BAP subheader.6. The method according to claim 1, wherein a backhaul RLC channel fortransmitting one or more data packets is configured by a donorcentralized unit (CU).
 7. An information transmission method comprising:receiving, at one or more integrated access and backhaul (IAB) nodes, anuplink (UL) transfer status from a IAB donor centralized unit CU,wherein the UL transfer status is transmitted after the IAB donor CUreceives a sequence numbers (SN) transfer message; retransmitting, atone of the one or more TAB nodes, according to the UL transfer status.8. The method according to claim 7, wherein the UL transfer statuscontains at least one of the receive status of a UL Packet DataConvergence Protocol (PDCP) service data unit (SDU) and UL COUNT valueof a first missing UL SDU.
 9. An information transmission method,comprising: transmitting, at one or more integrated access and backhaul(IAB) nodes, an end marker via GPRS Tunnelling Protocol (GTP)-U layer orF1AP message to a IAB donor centralized unit (CU) after receiving a stopindication in F1AP message.
 10. The method according to claim 9, whereinthe IAB donor CU sends the end marker to a second IAB donor CU.
 11. Themethod according to claim 1, wherein the one or more child nodes are oneor more User Equipment (UE).
 12. The method according to claim 1,wherein the one or more child nodes are one or more TAB Nodes.
 13. Awireless communication apparatus, comprising a processor configured toimplement a method, comprising sending, by an integrated access andbackhaul (IAB) node, uplink (UL) delivery status information to at leastone or more child nodes.
 14. The apparatus of claim 13, wherein the ULdelivery status information comprises sequence numbers (SNs) of one ormore packets that are received from one of the one or more child nodes,where the one or more packets have not been transmitted to a parent nodeor have not been confirmed as received by the parent node.
 15. Theapparatus of claim 14, wherein the UL delivery status information issent via a Backhaul Adaptation Protocol (BAP) sublayer control ProtocolData Unit (PDU) or BAP sublayer data PDU or a Radio Link Control (RLC)sublayer control PDU.
 16. The apparatus of claim 13, wherein the ULdelivery status information includes at least one of a RLC SN, a RLCchannel ID or Logical Channel (LC) ID, a backhaul (BH) RLC channel ID,or a BAP sublayer SN.
 17. The apparatus of claim 13, further comprising:sending, by the IAB node, one or more data packets that need to bere-transmitted to at least one of the one or more child nodes, whereinthe one or more data packets contain at least one of a source IAB node'sBAP address, an access node's BAP address and a flag in a BAP subheader.